1. Field of the Invention
This invention relates to molds employed in an injection molding apparatus for providing a continuous length of slide fastener chain or stringers by repeating the steps of clamping portions of a pair of continuous slide fastener tapes between a stationary mold and movable mold for injection molding, and then molding a plurality of slide fastener elements along the inner longitudinal edges of the tapes.
2. Cross-Reference to Other Application
In the molding of continuous slide fastener stringers through the use of an injection molds, the stringers are formed by repeating the steps of advancing intermittently a pair of long slide fastener tapes through the spacing between a stationary mold and movable mold, closing the molds on the tapes during the pauses in the advance of the tapes, injection molding fastener elements along longitudinal edges of the tapes, opening the molds after the molding and subsequently advancing the tapes. Such a continuous molding operation can be arranged to proceed in two different ways. In one case, the arrangement is such that the spacing between the last fastener element of a previously molded fastener element row and the first fastener element of a subsequently molded fastener element row will be the same as the spacing between adjacent ones of the fastener elements in each of the fastener element rows. In the other case, a predetermined spacing is provided between the previously molded and subsequently molded fastener element rows. The present inventor has disclosed in a separately filed application (Japanese Utility Model Application No. 92716/78; U.S. Ser. No. 054421) positioning means applicable in either of these cases. More specifically, the specification of the application teaches feeding from the molds a predetermined length of that portion of the tapes, namely the stringers, equipped with the molded fastener elements, subsequently moving back or retracting the tapes until and further retraction thereof is halted due to abutment between a runner, formed at the time the fastener elements are molded on the stringer tapes, and a positioning stopper erected on one of the molds, and then carrying out the next molding cycle after tensioning the tapes. This method does not involve any appreciable technical problem for the case in which the stringers are continuously formed leaving a space between the last fastener element of a previously molded fastener element row and the first fastener element of the subsequently molded fastener element row. However, a problem is encountered in the instance where this spacing between previously and subsequently molded fastener element rows is to be made equal to the fastener element pitch in these rows. The problem is that the use of the ordinarily employed flat stopper does not provide enough thickness of mechanical strength because the spacing between adjacent ones of the fastener elements is quite small. In addition, as the feeding of the stringers or retraction of the tapes is performed by rollers after the stringers have been removed from the molds, there is the possibility that the stringers or tapes will experience displacement laterally of the rollers and that the tapes will be clamped by the molds at an improper position during the succeeding molding cycle.